3 ms·

Making extremely low power consumption nodes is very satisfying, I made a very simple light sensor remote sensor node that could power itself from 50mg of vibra

Making extremely low power consumption nodes is very satisfying, I made a very simple light sensor remote sensor node that could power itself from 50mg of vibration acceleration a few years back on as part of my PhD in energy harvesting. The mast challenging part was getting the pic to draw the absolute minimal current and manage the power draw of all the other systems. The current draw was so low by the end that we had to use an electrometer with a 30 giga ohm (if I remember correctly) input impedance to accurately measure the current draw. Programming in asembly was a pain but I had a lot of help on that so not awful.

asmithmd1 9y ago
A high voltage meter input impedance will minimize the meter's effect on the circuit under test when measuring voltage, not current. For accurate current measurements, you want to measure the voltage drop across an accurate, low-value "shunt" resistor that carries all the current for your circuit.
- simonbarker87 9y ago
  Correct, so we used a high impedance voltage meter across a calibrated resistor in series with the circuit under test. It was 7 years ago I did the work and now rarely work hands on with electronics so I am hazy on the exact details but it’s all in the published journal paper, which, as always with science papers is now behind a paywall. UPDATE: I miss remembered, we used the high impedance electrometer to buffer the input of a National Instruments interface board so we could record the voltage build up across the storage capacitors, if you use a normal voltmeter the caps just discarge into the voltmeter and the charge never builds up enough to allow the micro controller to turn on, run the code it needs to and then go back to sleep. You land up with some really nice sawtooth wave forms with this method and, as the acceleration on the vibrational energy harvester increases, the frequency of the sawtooth changes proportionally up to a point where the system is transmitting all the time.

asmithmd1 9y ago

A high voltage meter input impedance will minimize the meter's effect on the circuit under test when measuring voltage, not current. For accurate current measurements, you want to measure the voltage drop across an accurate, low-value "shunt" resistor that carries all the current for your circuit.

simonbarker87 9y ago
Correct, so we used a high impedance voltage meter across a calibrated resistor in series with the circuit under test. It was 7 years ago I did the work and now rarely work hands on with electronics so I am hazy on the exact details but it’s all in the published journal paper, which, as always with science papers is now behind a paywall. UPDATE: I miss remembered, we used the high impedance electrometer to buffer the input of a National Instruments interface board so we could record the voltage build up across the storage capacitors, if you use a normal voltmeter the caps just discarge into the voltmeter and the charge never builds up enough to allow the micro controller to turn on, run the code it needs to and then go back to sleep. You land up with some really nice sawtooth wave forms with this method and, as the acceleration on the vibrational energy harvester increases, the frequency of the sawtooth changes proportionally up to a point where the system is transmitting all the time.